MPEG-2 systems perform packetizing and multiplexing processes for storing or transmitting the elementary stream (ES) generated by the video and audio encoder. Packetizing and multiplexing processes are largely classified into two types.
One is a process for producing a program stream (PS) to be stored in a storage medium; the other one is a process for producing a transport stream (TS) for network transmission or broadcasting.
When a scalable UHD video is being transmitted via the hybrid network, group information and transmission channel information of the scalable UHD video should be inserted into the program map table (PMT) which configures program specific information (PSI) in the MPEG-2 system.
According to an existing method for providing program information, only program information for a media being transmitted via a single channel broadcasting network has been provided through the PMT. However, in a converging environment, program information on a media which simultaneously uses both a broadcasting network, which is not a single channel of the broadcasting network, and an IP network, which is an augmentation channel, cannot be provided through a conventional PMT.
Accordingly, for a media having a hybrid transmission environment, transmission channel information on the media and group information between the media, which are being transmitted to each transmission channel, should be provided in an extended PMT.
Furthermore, future digital broadcasting is expected to develop into UHD broadcasting which requires high transmission capacity, multi-view 3D video broadcasting, and the like. Accordingly, standardization on MPEG media transport (MMT) is in progress as a study for a more efficient transmission format than the existing MPEG-2 TS.
MPEG media transport (MMT) is a new standard initiated to overcome the inefficiency occurring under the new environment wherein networks having transport stream (TS) of existing MPEG-2 system standards are ALL-IP networks.
The scope of MMT, which is being standardized, can be divided into three parts: encapsulation, delivery, and control. Hereinafter these will be investigated in detail.
In the encapsulation part, storage format for storing compressed media data or payload format for transmission are defined. There are three types of specific layers which are included in encapsulation: E.3 (MFU, i.e. Media Fragment Unit), E.2 (M-Unit), and E.3 (MMT Asset). In E.3 layer, a compressed media data is divided into slices or pictures and encapsulated. In E.2 layer, an access unit (AU) is produced by encapsulating E.3 layer. In E.1 layer, a transmission packet is produced by encapsulating E.2 layer.
In the delivery part, functions necessary for delivering an encapsulated media data from one network entity to other entity are defined. In the control part, functions are provided for controlling delivery and consumption of the media.
In the conventional method for providing layer information, maximum bits are inserted into the MFU header and provided without considering overlapping among the values representing a priority value (priority id), a resolution level (dependency id), a time level (temporal id), and a picture quality level (quality id). However, there is a high possibility of existence of overlapped information in layer information which contains scalable UHD video data.
When transmitted without considering such overlapped layer information, unnecessary bits are consumed since layer information containing larger data than layer information just containing actual scalable UHD video data is transmitted.
Thus, for a future MMT, a method that can provide group information on the scalable UHD video being transmitted under the hybrid transmission environment and channel information on each transmission environment is needed.
In addition, it is necessary to provide a method for inserting a layer identifier (layer id) representing layer information on each layer as separate information considering overlapping of layer information that is contained in the scalable UHD video data when the scalable UHD video data is being transmitted.